| 摘要 |
PROBLEM TO BE SOLVED: To produce highly pure spherical single crystals having uniform shapes without unevenness, and excellent in reproducibility of the characteristics by coating particles of spherical polycrystalline silicon produced by a high frequency thermal plasma method with thermal oxide membranes, heating and melting a part thereof, and recrystallizing the melted part while moving the melted part. SOLUTION: Spherical polycrystalline silicon having 0.1-5 mm, preferably 0.5-1 mm particle diameter is subjected to an etching treatment by an acid, and washed. The raw material silicon 8 of the spherical polycrystal is spread over a thermostable boat 10 made of quartz, and heated at 1200-1300 deg.C for 4-6 hr while charging wet O2 gas and N2 gas passed through a warm bath 15 heated by a heater 14 from a gas-charging opening 9 to a quartz tube 11 to provide spherical polycrystalline silicon coated with thermal oxide membrane having 0.5-5μm thickness. The polycrystalline silicon is partially melted in a temperature gradient of 10-50 deg.C/min at 1,420-1,430 deg.C, and recrystallized while moving the melted part under a condition of 0.7-1.5 mm/min growing rate.
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